I really think this just needs to be said again (P0420/P0430 code workaround)

2006 TRD Sport 230k miles. The P0420 had been coming on intermittently for the past year or so with the P0430 starting a few months back. I had no worries for awhile as I had 2 year tags. Well, they’re due at the end of this month so I finally had to put all the knowledge I gleaned from this and other sites to practice.

I decided on the Dorman (420009 part #) spark plug non-fouler method. It really couldn’t be easier.

I decided to get 2 packs just to be safe. Dorman 420009 18mm spark plug non-foulers so 4 total.

Put the non-fouler in your vice (or a way to really secure them good) and drill out the middle with a 1/2” bit. This size works perfect don’t use another.

Then put two together and unscrew your down stream O2 sensor that is related to the code or both like in my case.

Screw the non-foulers into the sensor bungs then put your O2 in there and plug them up.

Reset code with reader or unplug negative battery terminal for a minute and then re connect it and you should be good to go.

I mean $20 compared to $500-$1200. Sign me up.

 

Worked for me.

Aftermarket cats really benifit from this.

Due to overstringent requirements and under certain rare stringent excessive load conditions it'll kick a P0420. No longer an issue for me

 

I’m a visual learner. Got pics of it all put together?

 

Me to.

 

In the first two pics you can see the inside of the non-foulers. I’ve read some people just use one per side but when two are used it really isolates the O2 sensor.

You drill completely through the inner metal and open ip a 1/2” opening on the end. This allows the sensor to fit perfectly inside with just enough clearance for it to get a reading I reckon.

 

Eff it, crawling under the truck for a photo opportunity wasn’t that hard.

 

Do you drill both out or just the one near the O2?

 

Got it now, thanks @STacoL

But just real quick...does this solve a bad sensor or a bad catalytic converter? Did you know what actually failed on yours?

 

It doesn't solve anything other than keeping the truck from throwing the P0420 code.
The converter is still bad. It just raises the sensor up and limits exhaust getting to the sensor.
Since you have less exhaust gas getting to the sensor, it will read "cleaner".

You can't fix a bad sensor. It will throw a code even with the Anti-foulers.

Also.......

 

The 420/430 codes show up when the post-cat o2 sensor is not reading within the specified parameters. I.E. the cats aren’t cleaning the exhaust good enough.

This fix moves the O2 sensor further from the exhaust/reduces the amount of exhaust that is metered by the sensor. Thus making the ECM think the cats are doing their job properly. It fixes nothing other than fooling the car into thinking all is well.

New O2 sensors about $50 so if they were bad replacing them would be the best solution.

New cats on 2nd gen Tacos range from $400 all the way to about $1k plus labor to install them. There’s a lot of reports that cheapo cats (universal fit) do not work that great on these vehicles so there’s that to take into consideration too.

So for $20 and maybe 30 min under my truck (the sensors did not come out easily) this little fix is the shiznittlebam snip snap snappy.

I’m just hoping this will work long enough for me to get my inspections to get my plates. After that I got another two years to figure it out. General consensus though is I should be good to go for the foreseeable future.

 

Hah! This is a great trick. I run a cat simulator on my other car, basically this but with a little bit of cat material in it. Worth a try if these don't work for some reason on somebody's truck.

 

The use of MIL eliminators on Mustangs that have non-catted x/H pipes comes to mind.

Mine had them. I’m not sure if this was only because the vehicle had a custom tune on it or if it was doing the exact same thing, making the sensor think the exhaust has less oxygen in it. Only electronically instead of physically.

 

It makes the sensor more or less 'lazy". Thats not to say thats a bad thing. The EPA's overkill hypersensitive o.e. perameters are NOT real world sensitive. Another fine example of tree huggers shooting themselves in the foot. What happens is a p0420/p0430 prompts Joe diy'er to condem a GOOD o.e. cat, buy a cheap, underperforming aftermarket cat. Usually still getting these codes due to less internal catalyst components that can't keep up with o,e. (EPA) demands.

BTW IMO replacing the o2 sensor (unless it's truely bad) exagerates the above issue with quick sensitive readings. As described above the purpose of the extension is to remove slightly the sensor further away from the exhaust stream tomake less sensitive. Some o2 spacers even have a catalyst inthe tip. The anti foulers are a good grab at your local parts store quicky.

 

Just a follow up for the thing you should do if you get the P0420 Code.

Verify your truck doesn't have an outstanding recall for poor catalytic converters. You can do a vin search here:

https://www.toyota.com/recall

I bought my 2012 with the CEL on for O2 sensor a few years ago (I wouldn't recommend this BTW). Fixed the O2 sensor and got the P0420 code for bad cats. Checked with the recall site and sure-enough there was still an outstanding recall for my truck for possible bad cats. Toyota replaced the whole cat assembly free-of-charge. Even gave me a loner while it was in the shop.

Sometimes it's just best to be lucky.

 

The anti-foulers worked great for my 420/430 issue. Incidentally I recently got 22mpg driving home on a trip so I'm not sweating the mixture, OBD F/A ratio shows 14.6 the entire time.

 

I just drilled the one so the sensor would fit but I've yet to install mine.

 

So I just moved to IL and this is the reason for me needing to do all of this.

Funny thing is that in a year from this registration I’ll have to get my truck inspected where they put it on a dyno and measure the spent hydro carbons exiting the tail pipe…

We had to do that like 20 years ago in MO and that program only ran for a few years.

I have no problem with the EPA and really wish they made it tougher for people to pollute but at least make shit uniform across the board.

50 states 50 different protocols.

 

But the AF is derived in part from the downstream sensors, right? Or am I misremembering that

If so then that reading is no longer accurate

 

It is measured at the first sensor. The Air Fuel Sensor. The foulers only go on the rear sensors. And they only measure the output of the converters.

FWIW, Toyota uses lambda and on both banks. To get a good reading, you’d look at both banks.

Or have a single sensor down stream of both manifolds.

But anyways. No, the foulers won’t affect the a/f ratio.
.

 

I only mentioned that because my mileage nor the A/F mixture has changed after making the mod. So it doesn't appear that the anti-foulers "fouled" anything up except the systems ability to check the cat performance.